SSD or Virtual Memory? It’s possible?

I bought a MacMini, which configuration is: 1.4 GHz Intel Core i5 Dual-Cor, 4 GB 1600 MHz DDR3 and 256 GB SSD. Using the machine, I noticed it’s a little slow for my purpose. So I would like to know if buying an external SSD would give me more speed… would that be a possible solution? Also, is it possible to create a “virtual memory” on MacOSX? Thanks.